Extracting Fertilizer from a Clear Blue Sky

Nitrogen fixation in cereals has been a dream of scientists and farmers for a long time. If rice, wheat and maize are able to fix all of their nitrogen from the atmosphere in the same manner as soybean, it would have major financial and environmental benefits for the agricultural community.

Recent successes from IAEA-funded studies in Latin American countries (Uruguay and Brazil) using 15N methodology indicate that inputs of N fertilisers for cereal production can be substantially reduced by inoculating cereal crops such as maize and wheat with "endophytic diazotrops',
i.e. nitrogen fixing bacteria, which infect the interior such as stem, leaves and roots of cereals. Responses can be up to 30 % of yield, and over 50 kg of N fertiliser can be substituted by an inoculant which cost only about US$1.00 per ha.

Results with sugar cane under controlled conditions and in farming areas in Brazil showed that the N2-fixing bacteria, including Gluconacetobacter, Herbaspirillum and Burkholderia species within the plant roots and stems can actually contribute up to 40 % of the plant nitrogen requirement through fixing atmospheric nitrogen. Considering the
current use of 52 and 2338 million metric tonnes of nitrogen fertiliser in Uruguay and Brazil, respectively, the potential savings through biological nitrogen fixation (BNF) or the inoculation of N2-fixing bacteria on cereal crops could be enormous.

Transferring the BNF technology to maize and rice crops in Africa in combination with better soil and water management practices could help to improve the productivity and nutritional quality of rice and maize and realise the second Green Revolution in Africa.